Process Selection of Mineral Processing Bandung, 1 November 2012

Company Overview 1 General 2 Case Study 3

Company Overview  ANTAM At A Glance  Unit Operation  Exploration Overview  Summary of Development Projects 1

Company Overview ANTAM At A Glance* Government of Indonesia 65% 99.98% Antam is a vertically integrated, export- oriented, diversified mining and metals company We undertake all activities from exploration, excavation, processing through to marketing Operations spread throughout the mineral- rich Indonesian archipelago Possess large holdings of high quality reserves and resources Many licensed exploration areas and joint venture projects Public Subsidiaries 35% Bauxite & Alumina Based Company Precious Metals Based Company Nickel Based Company Investment Company Coal Based Company Mining Operator Iron, Steel & Stainless Steel CGA Processing Plant 80% 99.5% 99.15% 100% 99.5% 99.98% 99.98% 99.5% PT Indonesia Chemical Alumina (Indonesia) PT Borneo Edo International (Indonesia) PT Cibaliung Sumberdaya (Indonesia) Asia Pacific Nickel Pty., Ltd. (Australia) PT International Mineral Capital (Indonesia) PT Indonesia Coal Resources (Indonesia) PT Antam Resourcindo (Indonesia) PT Abuki Jaya Stainless Indonesia (Indonesia) Gold Mine & Processing Plant 99.5% 99.5% 75% 25% 99.98% 34% PT Dwimitra Enggang Khatulistiwa (Indonesia) PT Mega Citra Utama (Indonesia) PT Gag Nikel (Indonesia) PT Citra Tobindo Sukses Perkasa (Indonesia) PT Meratus Jaya Iron & Steel Indonesia (Indonesia) 50% Coal Mining Operator Sponge Iron Processing Plant PT Feni Haltim (Indonesia) Agriculture Company 99,5% FeNi Processing Plant PT Borneo Edo International Agro (Indonesia) *Does not include Antam’s minority joint ventures

Company Overview Summary of Development Projects (CAPEX Plan) South Kalimantan Sponge Iron Project (MJIS) Iron making smelter Capacity : 315,000 tonnes product pa Completion : 2012 Project Cost : US$150 million ANTAM Share : 34% FeNi Halmahera Project Ferronickel smelter Capacity : 27,000 tonnes Ni pa Completion : 2015 Project Cost : US$ 1.6 billion ANTAM Share : 100% SGA Mempawah Project Bauxite processing into SGA Capacity : 1.2 mmt of SGA pa Completion : 2015 Project Cost : US$1.0 billion ANTAM Share : 100% Partner : - Modernization & Optimation Pomalaa (MOP-PP) Nickel Capacity : 10,000 ton Ni pa (increase) Completion : 2014 Cost : US$ 486 million ANTAM Share : 100% Bauxite processing into CGA Capacity : 300,000 tonnes of CGA pa Completion : 2014 Project Cost : US$450 million ANTAM Share: 80% Partner : Showadenkko KK (JPN) CGA Tayan Project Nickel Mandiodo Project Capacity : 12,000 ton ni pa (10% Ni \ in product) Completion : 2016 Cost : US$398 million (incl. 4x25 MW CFPP) ANTAM Share : 100% Processing plant through PT AJSI Nickel Bauxite Iron ANTAM’s development projects are driven by a requirement to build downstream process capabilities in order to comply with new Indonesian mining laws

General  Definition  Factors in Process Selection 2 General  Definition  Factors in Process Selection

Definition Process selection: The goals: the systematic development of the optimum metal extraction route for a particular ore using the most appropriate technology The goals: Optimize project economics, principally a function of metal/mineral recovery, throughput rate, capital and processing cost. Develop a process that satisfies all of the project requirements, including environmental considerations.

Factors in Process Selection Geological Mineralogical Metallurgical Environmental Geographical Economic and Political

(1) Geological Factor (2) Mineralogical The grade and reserve of economic minerals in an orebody determine the type and scale of process technology that can be applied. The process selected must be able to cope with ore type variations that are inevitable, even after blending, such as ore hardness, mineral composition, alteration, degree of fracturing and clay content. (2) Mineralogical The mineralogical properties of an ore determine its response to the various process options and indicate the potential environmental impact of its treatment. The mineralogical characteristics are determined from the ore composition and textural properties. Such date is used in conjunction with metallurgical testwork results and information from other similar orebodies for process selection and flowsheet development.

(3) Metallurgical The metallurgical response of an ore to a proposed treatment scheme directly determines the economics of the process, or combination of processes used. The factors to be considered in the evaluation are: Recovery of valuable minerals. Quality of product, and the need for further processing. Treatment rate. Capital cost. Operating cost. Environmental impact. Technical risk. The factor 1-3 affect the revenues generated by the project, items 2-6 affects process costs, and 7 is the level of uncertainly associated with a process.

(4) Environmental Process selection must be considered the environmental impact that each unit process has on the following: water quality, air quality, land degradation, visual impact, noise, flora and fauna, rare and endangered species, and cultural resources. These are affected by the following aspects of chemical extraction processes: the types and amount of wasted produces (solids, liquids, and gases) the short and long term stability of waste products alteration of minerals and metal by the process the process water balance and the need for discharge the method of waste disposal and treatment

(6) Economic and Political (5) Geographical The location of the orebody and the proposed treatment facility may have an important effect on process selection. The main factors include: climate (rainfall, temperature ranges) water supply topography infrastructure availability of equipment, reagents and supplies communications, political environmental availability of skilled and unskilled labor sites of archaeological or religious importance (6) Economic and Political Economic and political factors which may affect process selection are many and varied. The most important of these are the price of the metals tax rates structures and the prevailing economic and political climate, both locally and worldwide.

Case Study  Nickel  Gold 3 Case Study  Nickel  Gold

NICKEL

Classification of Nickel Ore Classification of nickel ore from a metallurgical perspective SULPHIDE ORES OXIDE ORES 36% 64% Sulphide ores respond to concentration process. Sulphide ores mined at 1% nickel can be readily concentrated to 10% nickel. High Magnesia Ore processed (Saprolites) by smelting. High Iron, Low Magnesia ore (Limonite) recovered by selective reduction. Technical Paper, Nickel Production from Low Iron laterites Ore, RA Bergman, Toronto, 2003

Nickel Mineralogy Sumber: “Ullmann's Encyclopedia of Industrial Chemistry “, Derek G. E. Kerfoot, Sherritt Gordon Limited, Fort Saskatchewan, Alberta, Canada, 2000

Laterite Profile Sumber: “Nickel Extraction Technology Developments”, Roman Berezowsky, 2004, “Mineral Processing and Technology for Sustainable Mining”, Darma Ambiar

Sulphides Ore Processing Sumber : NICKEL MINE CAPACITIES AND COSTS Speech to International Stainless Steel Forum, 2nd Annual Meeting & Conference, Madrid 10th-12th May 1998 Adrian Gardner, Brook Hunt

Laterite Ore Processing Sumber : NICKEL MINE CAPACITIES AND COSTS Speech to International Stainless Steel Forum, 2nd Annual Meeting & Conference, Madrid 10th-12th May 1998 Adrian Gardner, Brook Hunt

Differences in Processing Sumber : NICKEL MINE CAPACITIES AND COSTS Speech to International Stainless Steel Forum, 2nd Annual Meeting &Conference, Madrid 10th-12th May 1998 Adrian Gardner, Brook Hunt

World Nickel Processing

Process Flowsheet

Flowsheet PAMCO PT INCO

Flowsheet Nippon Yakin Falconbridge

Flowsheet Cuba - Caron Process

Flowsheet Murrin Murrin - PAL Sumber : Murrin Murrin Process Flowsheet, Motteram, Ryan dan Weizenbach (1997)

GOLD

Classification of Gold Ore Classification of gold ore from a metallurgical perspective Free Milling Refractory yielding over 90% recovery under conventional and relatively straightforward flowsheet selection Those that is difficult to treat and give gold recoveries of less than 90%, in some cases much less than 50% Complex yielding acceptable recovery with the use of significantly higher chemical additions, mainly associated with base-metal mineralization

Classification of Gold Ore Metode pengolahan bijih emas (rute proses) sangat bergantung pada tipe bijih emas yang akan diolah. Terkait dengan proses pengolahannya, tipe bijih emas secara umum dapat diklasifikasikan sebagai bijih free, free milling dan refractory. Tipe yang pertama dan kedua relatif mudah untuk diolah dengan recoveri >90%, Bijih refractory adalah bijih yang sulit diolah (“difficult to treat”) dengan recovery <90%, bahkan seringkali < 50% bila digunakan proses sianidasi konvensional.

Classification of Gold Ore Bijih free milling: Partikel-partikel emas dapat dibebaskan dengan cara penggerusan (milling/grinding) umumnya hingga -200 mesh (74 m) ukuran partikel emas tidak terlalu halus. Bijih free milling umumnya merupakan bijih-bijih oksida (mineral-mineral utamanya adalah oksida, terutama silika/SiO2). Bijih free milling lebih mudah diolah rute proses: peremukan penggerusan leaching recovery.

Foto mikro emas tipe free dan free milling b. Free gold dlm mineral kuarsa (free milling) a. Free gold

Classification of Gold Ore Tipe-Tipe Bijih Refractory: Emas terjebak (terinklusi) di dalam mineral-mineral sulfida seperti pyrite (FeS2), arsenopyrite (FeAsS) yang bersifat non-porous. Partikel emas berukuran sangat halus dan sulit diliberasi dengan milling biasa. Bijih mengandung komponen-komponen yang reaktif (seperti pyrrhotite, arsenopyrite, marcasite) yang mengkonsumsi secara signifikan sianida dan oksigen yang dibutuhkan untuk reaksi pelarutan emas. Bijih preg-robbing Bijih emas mengandung material-material karbon, seperti karbon organik dan karbonat yang bersifat mengadsorpsi emas yang sudah ter-leaching.

Gold Mineralogy The principal gold minerals in ores are the native metal, Au-Ag tellurides, aurostibite, maldonite, and auricupride (Table A) Apart from the discrete gold minerals, gold occurs as a trace element in several common sulfide and sulpharsenide minerals (Table B)

Gold Mineralogy Generally, placers, quartz vein gold ores, oxidized ores,and silver-rich ores are free-milling. Iron sulfide ores and arsenic sulfide ores host different proportions of free-milling and refractory gold. Aurostibite (AuSb2), maldonite (Au2Bi), and telluride gold ores are often refractory. Common causes for refractory behavior of gold ores: Locked gold (“Refractory” Ores) Psysical locking Fine-grained gold inclussions in sulfides Chemical locking Gold minerals (tellurides, etc.) Submicroscopic gold in sulfides Reactive Gangue Mineralogy (“Complex” Ores) Leach-robbing ores Pyrrhotite Secondary copper sulfides As, Sb sulfides Preg-robbing ores Carbonaceous Clays?

Liberated and Locked Gold Photomicrographs showing the mode of occurrence of microscopic gold. (a) liberated; (b) and (c), attached to and locked in arsenopyrite (Apy); and (d) locked in pyrite (Py)

Hydrometallurgical Extraction of Gold The basic procedures of hydrometallurgical processes for the extraction gold: dissolution of gold into a leach solution purification and/or upgrading of the leach solution recovery of gold from the purified solution For refractory ore case, pre-treatment step is essential to enable the gold to be recovered The gold is effectively “locked” within the ore (locked in the sense that cyanide solution is unable to access the gold), either physically or chemically. Refractory ore pre-treatment options:

Process Route Proses komersial ekstraksi emas dari bijihnya dilakukan dengan: – Pelindian Sianidasi (Cyanidation Leaching) – Amalgamasi → terbatas pada tambang-tambang rakyat Penelitian banyak dikembangkan untuk mencari alternatif reagen pelindi (leaching agent) yang lebih ramah lingkungan, yaitu dengan: – Thiourea – Thiousulfat

Process Options

Merril Crowe Process Berkembang sebelum teknologi karbon aktif (pre-1980). Tidak efektif untuk bijih dengan grade emasnya rendah dengan kandungan base metals (Cu, Pb, Fe) yang tinggi, •Serbuk seng merupakan reagen yang terkonsumsi dalam proses presipitasi emas dan perak. Konsumsi reagen ini merupakan komponen utama biaya operasi pabrik. •Sementasi dengan serbuk seng harus dilakukan dalam larutan yang diklarifikasi (dijernihkan) dan dideaerasi (dihilangkan oksigen terlarutnya) terlebih dahulu → Perlu thickener, filter, vacuum tower →peralatan lebih banyak .

Flowsheet Merril Crowe

CIL, CIP, CIC Process CIL → efektif untuk bijih yang cenderung preg-rob. Karbon aktif telah ditambahkan dalam tangki pelindian. Contoh aplikasi: PT. Antam, UBPE Pongkor. •Berbeda dengan Proses Merril-Crowe, proses CIP dan CIL dapat merecover Au langsung dari lumpur (slurry). •Secara umum proses CIL mempunyai biaya modal (capital cost) yang lebih rendah dari CIP karena proses adsorpsi dilakukan sekaligus dalam tangki pelindian → jumlah tangki yang dibutuhkan lebih sedikit.

CIL, CIP, CIC Process Proses CIP lebih fleksibel daripada CIL. Jumlah tangki adsorpsi bisa ditambahkan sesuai dengan kebutuhan. •Tingkat abrasi karbon aktif lebih rendah, sehingga kemungkinan kehilangan emas akibat partikel karbon yang hancur dapat diminimalkan •Ukuran tangki untuk adsorpsi umumnya ¼ hingga 1/10 dari tangki pelindian. •CIC → untuk merecoveri emas-perak dari larutan hasil proses heap leaching atau untuk mengambil kembali emas yang terbawa dalam tailing cair (solution tailing).

Flowsheet CIP

CIP, CIL Vs. Merril Crowe Proses Merril Crowe memerlukan biaya (cost) yang lebih besar untuk proses pemisahan solid-likuid dan klarifikasi (thickener, filter, clarifier) hingga diperoleh filtrat jernih yang siap disementasi. Pada proses CIP dan CIL pemisahan solid dan liquid dilakukan dengan metode pengayakan (screening) yang lebih murah. Kehilangan Au dari proses CCD sekitar 1% dari kadar Au di pregnant solution (0.03 – 0.05 ppm) karena filtering dan settling yang tidak baik. Untuk proses CIP dan CIL yang baik, kehilangan Au dapat ditekan hingga 0.01 ppm. Dibandingkan Proses Merril-Crowe, CIP dan CIL bisa mengolah bijih berkadar Au lebih rendah.

Metode pengolahan bijih sulfida refractory Untuk pengolahan bijih sulfida refractory, telah diterapkan teknik-teknik sebagai berikut: Pre-aerasi, klorinasi Pemanggangan (roasting) untuk menghilangkan sulfur dari bijih yang dilepaskan dalam bentuk gas sulfur dioksida (SO2). Pelindian dengan bantuan bakteri (bioleaching), misalnya thiobaccilus ferrooxydans Pelindian pada temperatur dan tekanan tinggi (pressure leaching) Ultrafine grinding Flotasi - intensive leaching

Pre-treatment bijih sulfida refractory dengan roasting Cukup efektif menghilangkan sulfur dan melepaskan ikatan emas dari sulfur atau membuat bijih jadi porous karena sulfurnya keluar menjadi gas SO2. Bila bijih juga mengandung karbon (C) dan bersifat “double-refractory”, karbon juga dilepaskan dalam bentuk gas CO2. Pemanggangan (roasting) dilakukan dengan rotary kiln atau fluidized bed roaster. Biaya operasi tinggi, karena pemanggangan dilakukan pada suhu tinggi (> 800oC). Perlu minyak sebagai bahan bakar. Masalah lingkungan. Emisi gas SO2 mengotori lingkungan. Perlu investasi tambahan untuk penangkapan gas SO2.

Metode pengolahan bijih pregrob Bijih pregrobbing: Pemanggangan (roasting) untuk menghilangkan karbon dari bijih yang dilepaskan dalam bentuk gas karbon dioksida (CO2) Pretreatment bijih dengan blinding agent, misalnya dengan kerosene untuk mendeaktivasi material karbon dalam bijih sebelum dilakukan leaching. Resin in leach (RIL) Carbon in leach (CIL)→kurang efektif untuk bijih yang bersifat high pregrobber.

Flotasi → Intensive Leaching Prinsip: Emas yang terjebak atau berikatan dengan mineral-mineral sulfida seperi pyrite (FeS2), chalcopyrite (CuFeS2), galena (PbS) diapungkan terlebih dahulu dan dipisahkan dari mineral-mineral lain, terutama silika (SiO2) yang tidak terapung. Produk proses flotasi disebut KONSENTRAT. Kadar emas dalam konsentrat dapat ditingkatkan mulai dari 1,5 gram/ton hingga > 100 gram/ton. Selanjutnya konsentrat di-leaching dengan proses intensive leaching. Seringkali dikombinasi dengan konsentrasi gravitasi (misalnya dengan knelson, falcon, atau jig) dan prosesnya dikenal dengan “gravity-flotation-intensive leaching” (GFIL).

Flotasi → Intensive Leaching Berbeda dengan sianidasi biasa, intensive leaching dilakukan dengan konsentrasi sianida jauh lebih pekat. Sianidasi biasa dilakukan dengan konsentrasi sianida ± 0,2%. Intensive leaching dilakukan dengan konsentrasi ± 2%. Pada proses intensive leaching ditambahkan oksidator tambahan H2O2. Pada sianidasi biasa hanya diinjeksikan udara. Intensive leaching dilakukan pada rotating drum. Sianidasi biasa (selain heap leaching), umumnya dilakukan pada tangki silinder tegak, stasioner terbuka ke udara dengan pengaduk mekanik.

Flowsheet Intensive Leaching-Electrowinning dari GEKKO

Foto Inline Leach Reactor (ILR) GEKKO

Kelebihan bila bijih dikonsentrasi lebih dahulu Umpan proses sianidasi adalah konsentrat yang jumlahnya lebih sedikit Jumlah konsentrat = jumlah umpan / rasio konsentrasi Misal rasio konsentrasi (RoC) = 10, umpan bijih = 1000 t/hari, maka konsentrat yang disianidasi = 1000/10 = 100 t/hari Final tails (solids) =  900 t/hari. Final tails dari proses konsentrasi dapat langsung ditimbun di tailing storage facility (TSF). Final tails proses konsentrasi (flotasi + gravity) tidak kontak dengan sianid → apabila tersedia area untuk pemisahan TSF dari proses konsentrasi dan TSF dari proses sianidasi, kemungkinan dampak lingkungan dapat diminimalkan.

RIC → electrowinning

Kelebihan Ion exchange dibanding karbon aktif Mempunyai kapasitas adsorpsi dan kinetika adsorpsi yang lebih baik dari karbon aktif. Memiliki selektivitas adsorpsi terhadap base metals (Fe, Cu, Pb, Zn) yang lebih baik Memiliki ketahanan atrisi yang lebih baik dari karbon aktif. Resin penukar ion dapat langsung digunakan kembali sesudah proses elusi tanpa perlu diaktivasi kembali dengan proses pemanasan sebagaimana karbon aktif, sehingga mengurangi biaya untuk proses pemanasan. Contoh IX Resin komersial: Minix, Auric.

Electrowinning Au-Ag Larutan eluate yang kaya Au dan Ag dari proses elusi (desorpsi) karbon aktif/resin penukar ion dialirkan ke dalam sel electrowinning. Emas akan diendapkan pada permukaan katoda yang terbuat dari baja wool (steel wool) atau steel mesh. Endapan logam emas-perak bersifat loose (tidak menempel kuat) pada permukaan katoda dan berbentuk sludge/cake Proses pengendapan emas di katoda diikuti oleh oksidasi air di anoda sebagaimana ditunjukkan oleh reaksi elektrokimia sebagai berikut: Katoda : Au(CN)2- + e- → Au + 2CN- Anoda : 2H2O → 4H+ + O2 + 4e-

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